Metalorganic vapor phase epitaxy of ternary rhombohedral [formula omitted] Se3 solid solutions

Abstract

We studied the metalorganic vapor phase epitaxy (MOVPE) of (Bi1−xSbx)2Se3 solid solution films with a different Sb content on (001) Al2O3 substrates with thin ZnSe buffer layer in the range of temperatures 250–480°C. As-grown films were studied by atom force and scanning electron microscopy (AFM and SEM), Raman spectroscopy and X-ray diffractometry (XRD) techniques. To determine the elemental composition of the grown films, we used an energy dispersive spectrometer (EDS). The dependencies of the crystal structure of films on the growth temperature and Sb content (0≤x≤1) were explored. At different growth temperatures we obtained the following bismuth compounds: the films grown at the temperature of 370°C or lower consist of the pure Bi phase, whereas we got the Bi4Se3 phase at 380°C, the phase BiSe at 430°C and Bi2Se3 at the temperature of 460°C or above. We found out that at the temperature of 480°C the single-phase films of (Bi1−xSbx)2Se3 with rhombohedral and orthorhombic lattices are realized when x is less than 0.25 and greater than 0.935, respectively. For 0.25<x<0.935 the grown films are composites of rhombohedral and orthorhombic phases. At the temperature of 440°C we obtained films consisting of three rhombohedral phases (Bi1−xSbx)4Se3, (Bi1−xSbx) Se and Bi. The room temperature transport properties of rhombohedral samples were characterized using the Van der Pauw technique.